Zero sized reply squid error in Horde

Are you trying to resolve webmail error 'Zero sized reply squid error in Horde'?

This guide is for you.

Many of our customers approached us with this error message while trying to log in to Horde webmail. This error was seen after upgrading the Plesk version.

Here at Ibmi Media, as part of our Server Management Services, we regularly help our Customers to fix Webmail related errors.

In this context, we shall look into how to fix this Horde webmail error.

What triggers Horde webmail 'Zero sized reply squid error' ?

Before we get into the solution part of this error message, let us first see what causes this error to arise.

Generally, this error message appears when trying to log into the Horde webmail. It shows an error that the login has failed due to a bad user name or password and it might end with the error message "Zero sized reply squid error".

This happens after upgrading the Plesk version.

Also, some webmail Horde functionality may be broken (for example address book, calendar).

The cause of the problem is new horde system is trying to connect to localhost via the host's file.

How to fix Horde webmail 'Zero sized reply squid error' ?

One of our customers upgraded the Plesk version. Then he was not able to access the webmail and was receiving 'Zero sized reply squid error'.

Now let's take a look at how our Support Engineers resolve this error message.

The issue can be fixed following the below steps :

i. We tried to disable the Zend memory manager. In order to do this, we set the USE_ZEND_ALLOC environment variable to 0:

echo "export USE_ZEND_ALLOC=0"

ii. Then we restarted Apache by running the below command:

service httpd restart

If this doesn't work for you then try to disable ionCube.

[Need urgent assistance in fixing webmail errors? – We can help you. ]


This article will guide you on how to fix #Horde webmail 'Zero sized reply squid #error' by making changes to the system configuration file of #Apache. This error occurs in webmail in Plesk after the upgrade of the Plesk version.

#Squid is a caching and forwarding #HTTP web 3proxy. It has a wide variety of uses, including speeding up a web server by caching repeated requests, caching web, DNS and other computer network lookups for a group of people sharing #network resources, and aiding security by filtering traffic.

To fix this error:

1. Try to add to squid.conf an option:

server_http11 on

and restart squid.

2. Put the website to Proxy Exception.

For Linux Tutorials

We create Linux HowTos and Tutorials for Sys Admins. Visit us on

Also for Tech related tips, Visit or General Technical tips on